1. Field of the Invention
The present invention relates to a photomask material for formation of a photomask used in a manufacturing process of a semiconductor device.
2. Description of the Prior Art
FIGS. 1 and 2 show diagrams for explaining two types of conventional photomask materials which have been used in the manufacture of semiconductor devices. The conventional photomask material shown in FIG. 1 comprises a transparent glass substrate 1, such as silica, and a metal layer or film 2 such as chromium (Cr), tantalum (Ta) and the like which is formed, with about 1000 .ANG. in thickness, by means of evaporation or sputtering. Another conventional photomask material as shown in FIG. 2 comprises a transparent glass substrate 1 and a metal silicide film 3, such as a molybdenum silicide, a titanium silicide and the like which is also formed, with about 1000 .ANG. in thickness, by means of sputtering and the like.
In general, as a hard mask material for a semiconductor device, a chromium film is formed on a transparent glass substrate, with about 1000 .ANG. in thickness, by means of sputtering and the like. This is because such hard mask including a chromium film is useful for fining a patterning as a mask of high integration device and is advantageous as a hard mask having a high reliability, as compared with a conventional emulsion mask.
However, such a chromium film has less adhesive ability to the glass substrate, particularly, to silica glass. For example, after formation of chromium pattern, it is likely that the chromium film is stripped off from the substrate when washed. Metal silicide film using molybdenum, tantalum, titanium and the like serves to increase the joining ability to a transparent glass substrate 1. This is because bond of silicon included in the metal silicide is strongly coupled to a silicon included in the glass substrate containing SiO.sub.2 and Al.sub.2 O.sub.3. In addition, as compared with a chromium film, a metal silicide film is advantageous to a dry etching which is required, together with fining of a pattern, in view of etching speed.
Nevertheless, in case of a photomask material including a metal silicide film 3 formed on a transparent glass substrate 1, an amorphous metal silicide film is formed after formation of the film 3 by means of sputtering and the like, which makes the film quality non-uniform, and hence it is more likely that a very fine defect, such as a generation of pin hole, may be partially caused when washed or the like. Furthermore, flatness of mask is adversely affected by stress in the interface between the transparent glass substrate 1 and the metal silicide film 3.
Incidentally, Japanese Patent Application No. 42176/1981, filed Mar. 23, 1981 and laid open for public inspection Sept. 28, 1982 and Japanese Patent Application No. 42183/1981, filed Mar. 23, 1981 and laid open for public inspection Sept. 28, 1982 disclose that silicon layer and metal layer are deposited on a glass substrate so that a pattern of silicide is formed by an electron beam.